We propose to study two aspects of the crown gall tumor problem. The first of these is concerned with the development by plant tumor cells of a capacity for autonomous growth. The three aspects of this problem that we propose to investigate are: (1) the chemical nature and mode of action of a cell division-promoting factor that has been found to play a central role in the development of autonomy; (2) the nature and mode of action of a compound that appears to be related to cAMP(3':5') and that may be importantly involved in the regulation of cell division; (3) the nature of the changes in the membrane sytems that have been found to occur during the transition from a normal cell to a fully autonomous tumor cell. The second general area that we propose to investigate is concerned with the specific factors and cellular mechanisms that are involved in the suppression of and the recovery from the neoplastic state in the crown gall disease.